Medyo old yung idea that there's a bad guy tormenting the main characters throughout the season, but I still got affected because now I'm worried for Alexis! I really love the father-daughter dynamic and I'm kinda excited as to how they will treat it with this killer on the loose.

Gilles Marini - the former Brothers & Sisters star, Dancing with the Stars contestant and future Royal Pains guest star - will come on board the ABC hit as a magician.

According to TV Guide, the actor will portray Tobias Strange, one of the main suspects in the murder of a New York City magic-shop owner. He'll appear on the installment titled "Poof, You're Dead," slated to air in early 2011.

Late last week, Castle also announced that Laura Prepon will play the actress who brings Nikki Heat to the big screen.